1. Field of the Invention
The present invention relates to a camera, and more particularly to a camera which performs auto-focusing control by a passive system.
2. Description of the Related Art
For cameras which perform auto-focusing control in range finding, focus determination and the like by a passive system, what is provided with a device for emitting an auxiliary light for auto-focusing use is proposed because insufficient luminance of the subject prevents auto-focusing control from appropriately functioning. Also is proposed such a device using an electric flash as the source of the auxiliary light (Japanese Patent Application Publication Nos. 55-15154, 59-201009, 2000-111791 and 2000-338386, Japanese Patent No. 3139067 and so forth).
While an auxiliary light for auto-focusing use is emitted when, for instance, focusing is done by half pressing the shutter release button, where an electric flash is used for emitting this auxiliary light, if half pressing of the shutter release button and its cancellation are repeated, the electric power needed for real light emission for releasing the shutter may become insufficient. For this reason, it is necessary to charge the main capacitor after emitting an auxiliary light, but if the main capacitor is fully charged every time, when the shutter release button is fully pressed in the charging period, a longer time will be taken before the shutter can be released. Thus, since the shutter cannot be released during the charging period, even if the shutter release button is fully pressed, the user will have to wait until the charging is completed. The user will therefore feel awkward, and the camera itself will suffer the disadvantage of operating inconvenience.
An object of the present invention, attempted in view of this circumstance, is to provide a camera capable of charging the main capacitor after the emission of an auxiliary light for auto-focusing use with minimum operating inconvenience.
In order to attain the object stated above, the present invention is directed to a camera, comprising: a sensor having a plurality of light receiving elements which receive light from a subject in a range-finding area; an auto-focusing controller which performs auto-focusing control according to an output of the sensor; a charging device which charges a main capacitor; a light emitting device which is supplied with electric energy by the main capacitor and emits auxiliary light for auto-focusing use and auxiliary light for exposure use to the subject; a shutter release button which, when half pressed, causes auto-focusing control to be started according to the output of the sensor and, when fully pressed, causes shooting to be started; a light emission control device which causes the light emitting device to emit the auxiliary light for auto-focusing use when the shutter release button is half pressed and a desired output value is not obtained from the sensor; and a control device which, the auxiliary light for auto-focusing use emitted from the light emitting device in a state where the main capacitor is fully charged being supposed to be a first auxiliary light and the auxiliary light for auto-focusing use later emitted from the light emitting device when the shutter release button is half pressed again in a state where the main capacitor is not fully charged being supposed to be a second auxiliary light, following the emission of the first auxiliary light from the light emitting device, permits electric flash shooting by fully pressing the shutter release button after the charging of the main capacitor by the charging device as long as a first length of time and, following the emission of the second auxiliary light from the light emitting device, permits electric flash shooting by fully pressing the shutter release button after the charging of the main capacitor by the charging device as long as a second length of time longer than the first length of time.
According to the present invention, since the main capacitor is not always fully charged after an auxiliary light for auto-focusing use is emitted by half pressing the shutter release button, but it is charged only for a limited length of time, the operating convenience can be prevented from being deteriorated by charging.
Preferably, the control device, following the emission of the auxiliary light of an odd-numbered round from the light emitting device, permits electric flash shooting by fully pressing the shutter release button after the charging of the main capacitor by the charging device as long as the first length of time and, following the emission of the auxiliary light of an even-numbered round from the light emitting device, permits electric flash shooting by fully pressing the shutter release button after the charging of the main capacitor by the charging device as long as the second length of time.
According to the present invention, by setting that duration of charging to a required length of time for charging the main capacitor to a permissible minimum level to make possible electric flash shooting, impossibility of electric flash shooting due to insufficient charging can be reliably prevented.
Preferably, the first length of time is a length of time required for enabling the charging device to charge the main capacitor to a permissible minimum level to make possible electric flash shooting.
According to the present invention, by differentiating the length of time for charging according to whether or not the main capacitor is fully charged before auxiliary light emission, a more satisfactory performance can be achieved. Thus, since the remaining capacitance of the capacitor presumably is smaller after auxiliary light emission in a state in which it is not fully charged than after auxiliary light emission in a fully charged state, rational charging can be processed by charging the capacitor for a shorter period of time in the former case than in the latter case.
The present invention is also directed to a camera, comprising: a sensor having a plurality of light receiving elements which receive light from a subject in a range-finding area; an auto-focusing controller which performs auto-focusing control according to an output of the sensor; a charging device which charges a main capacitor; a light emitting device which is supplied with electric energy by the main capacitor and emits auxiliary light for auto-focusing use and auxiliary light for exposure use to the subject; a shutter release button which, when half pressed, causes auto-focusing control to be started according to the output of the sensor and, when fully pressed, causes shooting to be started; a light emission control device which causes the light emitting device to emit the auxiliary light for auto-focusing use when the shutter release button is half pressed and a desired output value is not obtained from the sensor; and a control device which, the auxiliary light for auto-focusing use emitted from the light emitting device in a state where the main capacitor is fully charged being supposed to be a first auxiliary light and the auxiliary light for auto-focusing use later emitted from the light emitting device when the shutter release button is half pressed again in a state where the main capacitor is not fully charged being supposed to be a second auxiliary light, following the emission of the first auxiliary light from the light emitting device, permits electric flash shooting by fully pressing the shutter release button after the charging of the main capacitor by the charging device to a permissible minimum level to make possible electric flash shooting and, following the emission of the second auxiliary light from the light emitting device, permits electric flash shooting by fully pressing the shutter release button after the charging of the main capacitor by the charging device to a fully charged level.
According to the present invention, since the main capacitor is not always fully charged after an auxiliary light for auto-focusing use is emitted by half pressing the shutter release button, but it is charged with a limited charging voltage, the operating convenience can be prevented from being deteriorated by charging. Also, by setting that charging voltage to a permissible minimum level to make possible electric flash shooting, impossibility of electric flash shooting due to insufficient charging can be reliably prevented.